Methods of integrating multiple gate dielectric transistors on a tri-gate (finFET) process

ABSTRACT

Two or more types of fin-based transistors having different gate structures and formed on a single integrated circuit are described. The gate structures for each type of transistor are distinguished at least by the thickness or composition of the gate dielectric layer(s) or the composition of the work function metal layer(s) in the gate electrode. Methods are also provided for fabricating an integrated circuit having at least two different types of fin-based transistors, where the transistor types are distinguished by the thickness and composition of the gate dielectric layer(s) and/or the thickness and composition of the work function metal in the gate electrode.

This is a Continuation application of Ser. No. 13/997,624 filed Jun. 24,2013, which is a U.S. National Phase application under 35 U.S.C. § 371of International Application No. PCT/US2011/067681 filed Dec. 28, 2011.

TECHNICAL FIELD

The present invention relates generally to the manufacture ofsemiconductor devices, semiconductor logic devices, and transistors. Inparticular, embodiments of the present invention relate to processes forfabricating a multiple fin-based devices with varied gate structures onthe same chip.

BACKGROUND

The desire for ever-smaller integrated circuits (IC) places enormousdemands on the techniques and materials used to construct the devices.Components of IC chips include solid-state logic devices (transistors)such as CMOS (complementary metal oxide semiconductor) devices. Recentlydeveloped fin-based transistors enable increased performance for asmaller device footprint. Different transistor applications havedifferent structure and performance requirements, for example, highspeed logic operations, low power usage, high voltage input output(I/O), and extremely high voltage. Novel processes are required toenable fabrication of multiple types of new fin-based transistors on asingle chip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D illustrate embodiments of dual-gate transistors, whereineach transistor has a different gate stack configuration.

FIGS. 2A-2B illustrate embodiments of triple-gate transistors, whereineach transistor has a different gate stack configuration.

FIGS. 3A-3B illustrate embodiments of quad-gate transistors, whereineach transistor has a different gate stack configuration.

FIGS. 4A-4I illustrate methods for forming a single IC having multipletransistors with different gate stack configurations.

FIGS. 5A-5I illustrate additional methods for forming a single IC havingmultiple transistors with different gate stack configurations.

FIGS. 6A-6G illustrate additional methods for forming a single IC havingmultiple transistors with different gate stack configurations.

FIGS. 7A-7E illustrate additional methods for forming a single IC havingmultiple transistors with different gate stack configurations.

FIG. 8 illustrates a computing device in accordance with one embodimentof the invention.

DETAILED DESCRIPTION

An integrated circuit (IC) structure comprising two or more fin-basedfield effect transistors, having different types of gate structures, anda method for forming the different types of transistors on a single chipare described. The present invention has been described with respect tospecific details in order to provide a thorough understanding of theinvention. One of ordinary skill in the art will appreciate that theinvention can be practiced without these specific details. In otherinstances, well known semiconductor processes and equipment have notbeen described in specific detail in order to not unnecessarily obscurethe present invention. Additionally, the various embodiments shown inthe figures are illustrative representations and are not necessarilydrawn to scale.

Embodiments of the present invention provide an integrated circuithousing a plurality of fin-based transistors having different types ofgate structures, and methods for manufacturing these different types ofdevices on a single circuit. The formation of ICs having a plurality oftransistor types can address divergent circuit requirements, such as,for example, high speed logic operation, low power usage, high voltageinput output (I/O), and extremely high voltage, which are desirableattributes for components of system-on-a-chip (SOC) integrated circuits.System-on-a-chip devices integrate a wide variety of circuit functions,such as processor cores, analog functions, and mixed signal blocks, ontoa single integrated circuit chip. Embodiments of the invention provideICs with transistors having different types of gate structures, eachcomprising one or two high k material gate dielectric layers, an oxide(SiO₂) layer, one or two work-function metal layers, a fill metal, andcombinations thereof. Transistors with different gate structures arecapable of providing performance characteristics that span a wide rangeof operating speeds, leakage characteristics, and high voltagetolerances. Methods of forming circuits comprising transistors withdifferent gate structures are also disclosed.

FIGS. 1A-1D illustrate embodiments of fin-based transistors located inan integrated circuit. Each integrated circuit has at least twodifferent transistor types that are distinguished at least by thethickness or composition of the gate dielectric and/or the compositionof the work function metal(s) employed in the gate electrode. Thetransistors may have other distinguishing features. Typically, anintegrated circuit having a plurality of different transistor types willhave a large number of instances of each type of transistor arranged invarious formats (e.g., arrays). For simplicity, one instance of eachtype of transistor is shown in FIGS. 1A-1D as an isolated transistor,although the transistors illustrated are typically found in variousplaces and arrangements in the integrated circuit chip in which they arelocated.

FIG. 1A illustrates a three-dimensional perspective view of twotransistors 101 and 102 formed on the same IC. FIG. 1B illustrates across-sectional view of transistors 101 and 102 as shown in FIG. 1A,taken through the channel regions 116 and gate structures 111A and 111Balong line A-A′. Fins 112 extend from semiconductor substrate 110 and,in embodiments, run the full length of substrate 110. In an embodiment,each transistor comprises one or more fins 112 separated by isolationregions 114. In an embodiment, each transistor comprises a gatestructure 111 that wraps around the side and top surfaces of a portionof each fin 112, defining a channel region 116. In an embodiment,transistor 101 comprises gate structure 111A, and transistor 102comprises gate structure 101B, as shown in FIG. 1A. Each fin 112 has apair of source/drain regions 118 disposed on opposite sides of channelregion 116, as shown in the embodiment illustrated by FIG. 1A. For aPMOS device, the source/drain regions are p-type doped and the channelregion is n-type doped. For an NMOS device, the source/drain regions aren-type doped and the channel region is p-type doped. The height of fins112 above isolation regions 114 ranges from 20 to 100 Å, and the widthof fins 112 range from 5 to 20 Å.

Each transistor gate structure 111A and 111B comprises a gate dielectric113 and a gate electrode 115, as shown in FIG. 1A. Each gate dielectric113 may comprise one or more dielectric layers, for example, a silicondioxide layer or a high k dielectric layer. The gate dielectric 113insulates the channel region 116 from the gate electrode 115 to reduceleakage and to set the device threshold voltage. Each gate electrode 115includes one or more work-function metal layers and may also include aconductive fill metal 140. A work function metal layer manages thebarrier height between the dielectric material and the fill metal,minimizing resistance at the metal-semiconductor interface, and settingthe work function of the device. The fill metal carries the bulk of thecharge that controls the transistor state, and typically is alower-resistance material than the work function metal(s).

The integrated circuit shown in FIGS. 1A-D has at least two differenttypes of transistors, 101 and 102 that are distinguished by thecomposition of the dielectric layers employed in the transistor gatestructure. In an embodiment of the invention, the gate structure oftransistor 101 comprises a gate dielectric having a high k dielectriclayer 121 and a gate electrode having both a work function metal layer131 and a fill metal 140, as shown in FIG. 1B. The type of gatestructure in transistor 101 enables use of the transistor for highperformance cores.

In an embodiment of the invention, high k dielectric layer 121 conformsto the side and top surfaces of the fins 112 and isolation regions 114that comprise transistor 101. In general, a high k dielectric layer is adielectric material having a dielectric constant greater than that ofsilicon dioxide. The dielectric constant of silicon dioxide is 3.9.Exemplary high k dielectric materials that may be used in high-kdielectric layer 121 include hafnium dioxide (HfO₂), hafnium siliconoxide, lanthanum oxide, lanthanum aluminum oxide, zirconium dioxide(ZrO₂), zirconium silicon oxide, titanium dioxide (TiO₂), tantalumoxide, barium strontium titanium oxide, barium titanium oxide, strontiumtitanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalumoxide, lead zinc niobate, and other materials known in the semiconductorart. High k dielectric layer 121 ranges from 10 to 50 Å thick. In anembodiment, high k dielectric layer is 30 Å thick.

Work function metal layer 131 conforms to the surface of high kdielectric layer 121. Exemplary metals that may be used in work functionmetal layer 131 include titanium nitride, tungsten nitride, tantalumnitride, titanium aluminum, tungsten, silicides and other materialsknown in the semiconductor art. Work function metal layer 131 rangesfrom 10 to 50 Å thick. In an embodiment, work function metal layer 131is 30 Å thick.

Fill metal 140 fills the gate structure opening defined by work functionmetal layer 131. Fill metal 140 may comprise materials including, forexample, metal gate materials, such as, hafnium, zirconium, titanium,titanium nitride, tantalum, aluminum, and combinations thereof.Additional materials include, metal carbides, such as, for example,titanium carbide, zirconium carbide, tantalum carbide, hafnium carbideand aluminum carbide. Further materials that may be used includeruthenium, palladium, platinum, cobalt, nickel, and conductive metaloxides, such as, for example, ruthenium oxide. Other materials arepossible.

In an embodiment, the gate structure of transistor 102 has a gatedielectric comprising both a silicon dioxide layer 125 and high kdielectric layer 121, and a gate electrode comprising both work functionmetal layer 131 and fill metal 140. In an embodiment, silicon dioxidelayer 125 is grown from the surfaces of fins 112. In another embodiment,silicon dioxide layer 125 is conformally deposited on fins 112 andisolation region 114. Silicon dioxide layer 125 may be from 5 to 100 Åthick. In an embodiment, silicon dioxide layer 125 is 30 Å thick. In anembodiment, high k dielectric layer 121 covers silicon dioxide layer 125within the gate structure, and together the two layers form the gatedielectric. In an embodiment, work function metal 131 covers high kdielectric layer 121, and fill metal 140 fills the opening lined by workfunction metal 131. As compared to the gate structure in transistor 101,the addition of silicon dioxide layer 125 to the gate dielectric enablesuse of transistor 102 for high voltage, input output (I/O) circuitapplications.

Typically, transistor structures 101 and 102 are at least partiallysurrounded by a dielectric material 150, as shown in FIG. 1B. In someembodiments dielectric material 150 is an interlayer dielectric (ILD)material, such as silicon dioxide or low k dielectric materials.Additional dielectric materials that may be used include carbon dopedoxide (CDO), silicon carbide, silicon nitride, organic polymers such asperfluorocyclobutane or polytetrafluoroethylene, fluorosilicate glass(FSG), and organosilicates such as silsesquioxane, siloxane, ororganosilicate glass.

In an embodiment, spacers 135 are located on sidewalls of the gatestructure 111. Spacers 135 are formed on the gate structure 111sidewalls adjacent to the source/drain regions 118, as shown in FIG. 1A,in order to isolate the gate structure 111 from epitaxial material grownon fins 112, and also to protect the channel region 116 during heavydoping of the source/drain regions. Spacers 135 may additionally beformed on the ends of each gate structure 111, as shown in FIG. 1B.Spacers 135 may be comprised of a suitable dielectric material, such as,for example, silicon nitride, silicon dioxide, silicon oxynitride, orother material known in the semiconductor art.

Another embodiment of the invention comprises at least two differenttypes of fin-based transistors, 101 and 103, where each transistor isdistinguished by the composition of the dielectric layers employed inthe gate structures, as shown in FIG. 1C. In an embodiment of theinvention, the gate structure of transistor 101 comprises a gatedielectric having a high k dielectric layer 121 and a gate electrodehaving both a work function metal layer 131 and a fill metal 140.

The gate structure of transistor 103 comprises a gate dielectric havingboth a high k dielectric layer 122 and high k dielectric layer 121, anda gate electrode having both work function metal layer 131 and fillmetal 140. In an embodiment, high k dielectric layer 122 is formed onthe fin surface. In an embodiment, high k dielectric layer 121 covershigh k dielectric layer 122. In an embodiment, work function metal layer131 covers high k dielectric layer 121. In an embodiment, fill metal 140completes the gate structure by filling in the gate structure openingdefined by work function metal layer 131. In an embodiment, high kdielectric layer 122 has a different composition or thickness than highk dielectric layer 121. As compared to the gate structure in transistor101, the addition of high k dielectric material 122 reduces gate leakagewhile increasing the threshold voltage, enabling use of transistor 103for low-power circuits or applications. High k dielectric layer 122 maybe any of the materials listed above with respect to high k dielectriclayer 121. High k dielectric layer 122 ranges from 10 to 50 Å thick. Inan embodiment, high k dielectric layer 122 is 30 Å thick.

Another embodiment of the invention comprises at least two differenttypes of fin-based transistors, 101 and 104, located on a singleintegrated circuit, where each type of transistor has a different gatestructure, as illustrated by FIG. 1D. In an embodiment of the invention,transistors 101 and 104 are distinguished by the composition of thework-function metal(s) employed in each gate electrode. In a specificembodiment, the gate structure of transistor 101 comprises a gatedielectric having a high k dielectric layer 121 and a gate electrodehaving both a work function metal layer 131 and a fill metal 140.

In an embodiment, the gate structure in transistor 104 comprises a gatedielectric having high k dielectric layer 121 and a gate electrodehaving a work function metal layer 132, work function metal layer 131and fill metal 140. In an embodiment, high k dielectric layer 121 coversthe fins 112. In an embodiment, work function metal layer 132 covershigh k dielectric layer 121. In an embodiment, work function metal layer131 covers work function metal layer 132. In an embodiment, fill metal140 fills the gate structure opening defined by work function metallayer 131. In an embodiment, work function metal layer 132 in transistor104 has a different work function than work function metal layer 131.The addition of work function metal 132, as compared to the gatestructure in transistor 101, increases the threshold voltage fortransistor 104 and reduces gate leakage, enabling use of transistor 104for low-power circuits or applications. Work function metal layer 132may be any of the materials listed above with respect to work functionmetal layer 131. Work function metal layer 132 may be from 10 to 50 Åthick. In an embodiment, work function metal layer 132 is 30 Å thick.

The embodiments illustrated by FIGS. 2A-B comprise three or more typesof fin-based transistors on a single integrated circuit, where each typeof transistor has a different gate structure. Typically, an integratedcircuit having a plurality of different types of transistors will have alarge number of instances of each type of transistor arranged in variousformats (e.g., arrays). For simplicity, one instance of each type oftransistor is shown in the figures as an isolated transistor, althoughthe illustrated transistors are typically found in various places andarrangements on the integrated circuit chip in which they are located.

The integrated circuit shown in FIG. 2A has at least three differenttypes of transistors, 201, 202, and 203 that are distinguished by thethickness or composition of the dielectric layers employed in the gatestructure, according to an embodiment of the invention. In anembodiment, the gate structure in transistor 201 comprises a gatedielectric having high k dielectric layer 221 and a gate electrodehaving both a work function metal layer 231 and a fill metal 240.Transistor 201 may be used for high performance processor cores. In anembodiment, the gate structure in transistor 202 comprises a gatedielectric having both a silicon dioxide layer 225 on the fin surfaceand high k dielectric layer 221 over silicon dioxide layer 225. In anembodiment, transistor 202 further comprises a gate electrode havingwork function metal layer 231 and fill metal 240. The addition ofsilicon dioxide layer 225 reduces leakage and increases the thresholdvoltage, as compared to transistor 201, enabling use of transistor 202for high-voltage input output (I/O) circuits or applications. In anembodiment, the gate structure of transistor 203 comprises a gatedielectric having both a high k dielectric layer 222 on fins 212 andhigh k dielectric layer 221 over high k layer 222. In an embodiment,transistor 202 further comprises a gate electrode having both workfunction metal layer 231 and fill metal 240. In an embodiment, high kdielectric layer 222 has a different composition than high k dielectriclayer 221. In another embodiment, high k dielectric layer 222 has adifferent thickness than high k dielectric layer 221. The addition ofhigh k dielectric layer 222 to the gate structure reduces leakage, ascompared to transistor 201, enabling use of transistor 203 for low-powercircuits.

The integrated circuit illustrated in FIG. 2B has at least threedifferent types of transistors, 201, 202 and 204, that are distinguishedby the composition or thickness of the dielectric layers and/or thecomposition of the work-function metals employed in the transistor gatestructure. In an embodiment, the gate structure in transistor 201comprises a gate dielectric having high k dielectric layer 221 and agate electrode having both a work function metal layer 231 and a fillmetal 240. Transistor 201 is designed to be used for high performanceprocessor cores. In an embodiment, the gate structure in transistor 202comprises a gate dielectric having both a silicon dioxide layer 225 onfins 212 and high k dielectric layer 221 on silicon dioxide layer 225.In an embodiment, transistor 202 further comprises both a gate electrodehaving work function metal layer 231 and fill metal 240. The addition ofsilicon dioxide layer 225 reduces leakage and increases the thresholdvoltage, as compared to transistor 201, enabling use of transistor 202for high-voltage input output (I/O) circuits or applications. In anembodiment, the gate structure of transistor 204 comprises a gatedielectric having high k dielectric layer 221 and a gate electrodehaving a work function metal layer 232, work function metal layer 231 onwork function metal layer 232, and fill metal 240. In an embodiment,work function metal 232 has a different work function than work functionmetal layer 231. The addition of work function metal layer 232 reducesleakage, as compared to transistor 201, enabling use of transistor 204for low power circuits or applications.

Circuits comprising at least four types of fin-based transistors, whereeach type of transistor has a different gate structure, are illustratedin FIGS. 3A-C, according to embodiments of the invention. Theembodiments comprising four types of transistor gate structures, asillustrated in FIGS. 3A-B, are extensions of the three-type transistorembodiments illustrated in FIGS. 2A-B, and may be fabricated withoutincurring additional processing steps.

The integrated circuit shown in FIG. 3A has at least four differenttypes of transistors, 301, 302, 303 and 305 that are distinguished bythe thickness or composition of the dielectric layers employed in thegate structure. In an embodiment, the gate structure in transistor 301comprises a gate dielectric having a high k dielectric layer 321, and agate electrode having both a work function metal layer 331 and a fillmetal 340. Transistor 301 is designed to be used for high performanceprocessor cores. In an embodiment, the gate structure in transistor 302comprises a gate dielectric having both a silicon dioxide layer 325grown on fins 312 and high k dielectric layer 321 over the silicondioxide layer 325. In an embodiment, transistor 302 further comprises agate electrode having both work function metal layer 331 and fill metal340. Transistor 302 is designed to be used for high-voltage input output(I/O) circuits. In an embodiment, the gate structure in transistor 303comprises a gate dielectric having both a high k dielectric layer 322 onthe fin surface and high k dielectric layer 321 over high k dielectriclayer 322, and a gate electrode having both work function metal layer331 and fill metal 340. In an embodiment, the composition of high kdielectric layer 322 is different than that of high k dielectric layer321. In another embodiment, the thickness of high k dielectric layer 322is different than that of high k dielectric layer 321. Transistor 303 isdesigned to be used for low-power circuits.

In an embodiment, the gate structure of transistor 305 comprises a gatedielectric having silicon dioxide layer 325 on the fins, high kdielectric layer 322 over silicon dioxide layer 325, and high kdielectric layer 321 over high k dielectric layer 322. In an embodiment,high k dielectric layer 322 has a different composition than that ofhigh k dielectric layer 321. In another embodiment, high k dielectriclayer 322 has a different thickness than that of high k dielectric layer321. In an embodiment, transistor 305 further comprises a gate electrodehaving work function metal layer 331 and fill metal 340. As compared tothe high-performance gate structure in transistor 301, the additions ofsilicon dioxide layer 325 and high k dielectric layer 322 increase thethreshold voltage of transistor 305, such that transistor 305 may beused for circuits requiring extremely high voltages.

Another embodiment of a circuit having multiple types of transistors isillustrated by FIG. 3B. The integrated circuit has at least four typesdifferent transistors, 301, 302, 304 and 306, that are distinguished atleast by the thickness or composition of the dielectric layers and/orthe composition of the work function metals employed in the gatestructure. In an embodiment, the gate structure in transistor 301comprises a gate dielectric having a high k dielectric layer 321 and agate electrode having both a work function metal layer 331 and a fillmetal 340. Transistor 301 is designed to be used for high performanceprocessor cores. In an embodiment, the gate structure in transistor 302comprises a gate electrode having both a silicon dioxide layer 325 grownon fins 312 and high k dielectric layer 321 over silicon dioxide layer325. In an embodiment, transistor 302 further comprises a gate electrodehaving both work function metal layer 331 and fill metal 340. Transistor302 is designed to be used for high-voltage input output (I/O) circuits.In an embodiment, the gate structure in transistor 304 comprises gatedielectric having a high k dielectric layer 321 and a gate electrodehaving a work function metal layer 332 layer, work function metal 331layer over the work function metal layer 332 layer, and fill metal 340.In an embodiment, work function metal layer 332 has a different workfunction than work function metal 331. Transistor 304 is designed to beused for low-power circuits.

In an embodiment, the gate structure in transistor 306 comprises a gatedielectric having both silicon dioxide layer 325 grown on fins 312 andhigh k dielectric layer 321 over silicon dioxide layer 325. In anembodiment, transistor 306 further comprises a gate electrode havingwork function metal layer 332, work function metal layer 331 over workfunction metal layer 332, and fill metal 340. In an embodiment, workfunction metal layer 332 has a different work function than workfunction metal layer 331. As compared to the high-performance gatestructure in transistor 301, the additions of silicon dioxide layer 325and work function metal layer 332 increase the threshold voltage oftransistor 306, such that transistor 306 may be used for circuitsrequiring extremely high voltages.

With respect to the previously described embodiments, it should be notedthat it is also possible to vary other device characteristics such asthe width of the gate, the width of the channel region, and the types ofsources and drains used to achieve specific transistor properties, as isunderstood by those of skill in the art.

In manufactured devices, layers of materials can deviate in appearancefrom the simplified illustrations provided herein for clarity, and canbe, for example, slightly thicker or thinner in areas. Additionally,what is described here as a “layer” of material may be made up of aplurality of layers of the material that essentially function as onelayer.

FIGS. 4A-I describe an embodiment of a method for the formation ofmultiple types of fin-based transistor gate structures. The method isuseful for forming integrated circuits comprising different types offin-based transistors on the same chip, wherein the transistors have atleast two different gate dielectric structures. An integrated circuitchip typically comprises multiple copies of the same transistor invarious locations on the substrate, however, one of each type oftransistor is shown in FIGS. 4A-I for clarity.

A substrate 410 having fins 412 is provided. In an embodiment of theinvention, fins 412 are formed from a bulk monocrystalline substrate.Substrate 410 and fins 412 can be formed of any well known semiconductormaterial, such as but not limited to silicon, germanium, silicongermanium, and III-V combinations including GaAs, InSb, GaP, and GaSb.The lower portions of fins 412 are separated by isolation regions 414 toprevent leakage from the fins, as shown in FIG. 4A. In an embodiment,isolation regions 414 comprise a dielectric material such as silicondioxide. In another embodiment, fins 412 are formed from asemiconductor-on-insulator (SOI) substrate comprising a lower bulksubstrate, a middle insulation layer, and a top monocrystalline layer.Fins 412 are formed from the top monocrystalline layer, and the middleinsulation layer forms an isolation region. The height of fins 412extending above isolation regions 414 range from 20 to 100 Å. The widthof fins 412 range from 5 to 20 Å.

Next, silicon dioxide layer 425 is formed on the surface of fins 412extending above isolation regions 414. In an embodiment, silicon dioxidelayer 425 will form a portion of the gate dielectric for the transistorformed on gate region 492. In an embodiment, silicon dioxide layer 425will subsequently be removed from gate region 491 prior to formingadditional gate structure components. In a specific embodiment, silicondioxide layer 425 is grown from the surfaces of fins 412. In anotherspecific embodiment, silicon dioxide layer 425 is blanket deposited byany method that enables conformal deposition on the fins 412 in the gateregions, such as chemical vapor deposition (CVD) or atomic layerdeposition (ALD). Silicon dioxide layer 425 may be grown or deposited toa uniform thickness. In an embodiment, silicon dioxide layer 425 is 30 Åthick.

The subsequent etching process to remove silicon dioxide layer 425 fromgate region 491 involves two sacrificial layers that protect portions ofsilicon dioxide layer 425 that will form active components of the deviceformed in gate region 492. In an embodiment of the invention, anembedded etch stop layer 442 is blanket deposited over the surface ofthe substrate, and a sacrificial silicon dioxide layer 443 isconformally formed over embedded etch stop layer 442. In an embodimentof the invention, embedded etch stop layer 442 and sacrificial silicondioxide layer 443 will not form active components of the transistors.Embedded etch stop layer 442 and silicon dioxide layer 443 may each bedeposited by any method suitable for forming a conformal layer, such asCVD or ALD. In an embodiment, embedded etch stop layer 442 is a materialthat is etched at a slower rate as compared to that of silicon dioxidewhen both are etched by a selected etch chemistry. In an embodiment,embedded etch stop layer 442 is silicon nitride.

Both embedded etch stop layer 442 and silicon dioxide layer 443 are eachformed to a uniform thickness. The thicknesses of the embedded etch stoplayer 442 and silicon dioxide layer 443 are each selected such that atimed etch will remove each layer in approximately the same time. In anembodiment, an HF etching process is used. HF etches silicon dioxide ata faster rate than silicon nitride, and therefore, in an embodiment,sacrificial silicon dioxide layer 443 is thicker than embedded etch stoplayer 442. In an embodiment, sacrificial silicon dioxide layer 443 isthe same thickness as silicon dioxide layer 425. In an embodiment,embedded etch stop layer 442 is 10 Å thick. In an embodiment, silicondioxide layer 443 is 30 Å thick.

Next, sacrificial silicon dioxide layer 443 is removed from the surfaceof gate region 491 using a photolithographic etch process. In anembodiment, a photoresist material is formed over the structure surface.The photoresist is photolithographically patterned so that photoresist455 covers gate region 492, as shown in FIG. 4C, where a gate structurecomprising silicon dioxide layer 425 will subsequently be formed. Theexposed portion of silicon dioxide layer 443 is then etched from gatestructure 491. Silicon dioxide layer 443 may be etched by any suitableetching process, such as a wet etch. The wet etch comprises, forexample, HF. The HF etch may have a concentration from 50:1-200:1. In anembodiment, silicon dioxide layer 443 is fully or nearly fully etchedfrom the surface of gate region 491 in 50 seconds.

After the etching of silicon dioxide layer 443, photoresist 455 isremoved from the structure surface, as shown in FIG. 4D. In general,photoresists are removed by well known processes in the semiconductorindustry. Photoresists can be removed, for example, through dry plasmaprocesses. The resist is removed in an oxygen plasma processes,frequently called ashing, designed to remove organic residues. Theplasma is generated, for example, by microwave, RF (radio frequency), orUV ozone sources. Alternately, the photoresist can be removed using asolvent or mixture of solvents.

Next, sacrificial gate material 454 is blanket deposited over thestructure surface, according to the embodiment illustrated in FIG. 4E.Sacrificial gate material 454 is formed to a thickness desired for thegate height. Sacrificial gate material 454 is then patterned and etchedto form sacrificial gate structures 456 over gate regions 491 and 492,so that active gate structures may subsequently be formed by a gatereplacement process. Deposition, patterning, and etching of sacrificialgate material are well known in the semiconductor art. The sacrificialgate structures 456 are patterned into the same shape and at the samelocation where the subsequently formed gate electrode and gatedielectric are to be formed. In an embodiment of the present invention,the sacrificial gate electrode material is formed from a material suchas silicon nitride or polysilicon. Following the formation ofsacrificial gate structures 456, fins 412 may be doped, for example, bytip implantation or halo implantation, as is well-known in the art.

Next, if desired, dielectric sidewall spacers 435 may be formed on thesidewalls of sacrificial gate structures 456. Sidewall spacers are usedto isolate the gate structure from epitaxial semiconductor material thatmay be grown on the source/drain regions of the fins, as shown in FIG.1A, but spacer material may additionally form on other sidewalls of thegate structure, as shown in FIG. 4F. Sidewall spacers 435 can be formedby any well known technique, such as, for example, by blanket depositinga conformal sidewall spacer dielectric over the substrate, and thenanisotropically etching to remove the dielectric spacer material fromhorizontal surfaces while leaving spacer material on vertical surfaces.The spacers 453 may be silicon nitride, silicon oxide, siliconoxynitride, silicon carbide, CDO or a combination thereof. In anembodiment, an overetch is used to remove spacer material from thesidewalls of fins 412 to enable subsequent growth of an epitaxial layeron the fin surface, doping of the source/drain region, and/or formationof source/drain contacts.

Next, a dielectric material 450 is blanket deposited over the substrate.The dielectric material is formed to a thickness sufficient tocompletely cover the substrate including sacrificial gate structure 456.The dielectric 450 is formed of a material that can be selectivelyetched with respect to the sacrificial gate material. That is, thedielectric is formed of a material whereby the sacrificial gatestructure 456 can be removed without significantly etching away thedielectric 450. After blanket deposition, the dielectric material 450 isplanarized, such as by chemical mechanical planarization (CMP), untilthe top surface is planar with the sacrificial gate structure 456.

The sacrificial gate structure 456 is then etched away to enableformation of the gate structures in gate regions 491 and 492.Sacrificial gate structures 456 may be removed using a wet or dry etchprocess. The etch process exposes underlying embedded etch stop layer442 surface on gate region 491 and underlying sacrificial silicondioxide layer 443 surface on gate region 492, as shown in FIG. 4G.

In an embodiment, an additional etch process removes embedded etch stoplayer 442 and silicon dioxide layer 425 from gate region 491 and alsosacrificial silicon dioxide layer 443 and embedded etch stop layer 442from gate region 492. In an embodiment, a selective etch is used. Inanother embodiment, a timed wet etch is used. In an embodiment, thetimed wet etch may comprise HF. In a specific embodiment, the HF etchesembedded etch stop layer 442 material at a faster rate over thesacrificial silicon dioxide 443 material. The etch process has, in anembodiment, a selectivity of 3:1. The HF etch may have a concentrationfrom 50:1-200:1. Because the thickness of each sacrificial layer hasbeen selected based on the rate at which HF etches the material, bothembedded etch stop layer 442 and silicon dioxide layer 425 on gateregion 491 are etched completely or nearly completely by the HF in thesame amount of time that sacrificial silicon dioxide layer 443 andembedded etch stop layer 442 are etched by the HF from gate region 492.

In an embodiment, silicon dioxide layer 425 remains on gate region 492,where it will form part of the gate dielectric. As such, silicon dioxidelayer 425 has been formed on gate region 492, without being exposedphotoresist, which may contaminate active device layers. This formationof a pristine silicon dioxide layer will improve the performance andreliability of the device over that of devices where active layers arepatterned directly using a photolithography process.

Next, a high-k dielectric layer 421 is conformally deposited over thesubstrate surface to a uniform thickness according to an embodiment ofthe invention. In an embodiment, high k dielectric material 421 coversthe top surface and sidewalls of fins 412 in gate region 491 andconforms to the silicon dioxide layer 425 surface on gate region 492. Inan embodiment, high k dielectric layer 421 will form part of the gatedielectric in the gate structures formed in both gate regions 491 and492. In an embodiment, the high k dielectric material is formed by aconformal process, such as CVD or ALD, to ensure contact with the finsurfaces in gate region 491 and the underlying silicon dioxide layer 425in gate region 492. High k dielectric layer 421 may be any suitable highk dielectric material, such as described above with respect to high kdielectric layer 121 in FIG. 1A. High k dielectric layer 421 may be from10 to 50 Å thick. In an embodiment, high k dielectric material 421 is 30Å thick.

Next, a gate electrode is formed in each gate region, over the gatedielectric. The gate electrode may comprise one or more work functionmetal layers and a fill metal. In an embodiment, work function metal 431is conformally deposited over the substrate to a uniform thickness. Workfunction metal 431 sets the work function for the device, and minimizesresistance at the metal-semiconductor interface between the gatedielectric and the gate electrode. Work function metal 431 is formed bya conformal process, such as CVD or ALD to ensure contact with theunderlying high k dielectric layer 421 in both gate regions 491 and 492.Work function metal layer 431 may be any suitable work function metal,such as described above with respect to work function metal layer 131 inFIG. 1A. Work function metal layer 431 may be from 10 to 50 Å thick. Inan embodiment, work function metal layer 431 is 30 Å thick.

A fill metal 440 is then blanket deposited over work function metal 431to a thickness sufficient to fill the gate structure openings in gateregions 491 and 492. Metal gate 440 may be formed by any suitableprocess, such as CVD, ALD, or physical vapor deposition (PVD). The metalgate material may be any suitable gate electrode material, such asdescribed above with respect to FIG. 1A.

The metal gate 440, work function material 431, and high k dielectriclayer 421 are then chemically mechanically planarized until the topsurface of the dielectric layer 450 is revealed as shown in FIG. 4I.Once the gate electrode material and gate dielectric material arepolished back or removed from the top dielectric material 450, a gatestructure has been formed.

Thus, two transistors 401 and 402 are formed, each with a different gatestructure. In an embodiment, Transistor 401 comprises a gate dielectrichaving a high-k material 421 and a gate electrode having both a workfunction metal 431 and fill metal 440. Transistor 401 may be used forhigh-performance processor cores. In an embodiment, transistor 402comprises a gate dielectric having both a silicon dioxide layer 425 andhigh k dielectric layer 421 and a gate electrode having work functionmetal layer 431 and fill metal 440. The addition of silicon dioxidelayer 425 to the gate dielectric, as compared to the gate dielectric oftransistor 401, enables use of transistor 402 for high voltageinput-output (I/O) circuits or applications.

FIGS. 5A-I illustrate another method for forming integrated circuitscomprising two types of transistors that have different gate structures.An integrated circuit chip typically comprises multiple copies of thesame transistor in various locations, however, one of each type oftransistor is shown in FIGS. 5A-I for clarity.

A substrate 510 having fins 512 is provided, as shown in FIG. 5A. In anembodiment, substrate 510 and fins 512 are monocrystalline silicon. Fins512 are separated by isolation regions 514, which may comprise adielectric material such as, for example, silicon dioxide. Methods forforming the structure shown in FIG. 5A are known in the art ofsemiconductor manufacturing.

Next, silicon dioxide layer 525 is formed on the surface of thestructure. In an embodiment of the invention, silicon dioxide layer 525will form part of the gate structure subsequently formed in gate region592. In a specific embodiment, silicon dioxide layer 525 is grown fromthe surfaces of fins 512. In another specific embodiment, silicondioxide layer 525 is deposited by any method that enables conformaldeposition on the horizontal and vertical surfaces of the gate region,such as CVD or ALD. In an embodiment, silicon dioxide layer 525 is 30 Åthick.

Sacrificial gate structures are then formed so that active gatestructures may subsequently be formed by a gate replacement process,according to an embodiment of the invention. In an embodiment,sacrificial gate material 554 is blanket deposited over silicon dioxidelayer 525, as shown in FIG. 5B. Sacrificial gate material 554 is formedto a thickness desired for the gate height. Sacrificial gate material554 is then patterned and etched to form sacrificial gate structures 556over gate regions 591 and 592. Deposition, patterning, and etching ofsacrificial gate material are well known in the semiconductor art. Thesacrificial gate structures 556 are patterned into the same shape and atthe same location where the subsequently formed gate electrode and gatedielectric are to be formed. In an embodiment of the present invention,sacrificial gate structure 556 is formed from a material such as siliconnitride or polysilicon. Following the formation of sacrificial gatestructures 556, fins 512 may be doped, for example, by tip implantationor halo implantation, as is well-known in the art.

Next, if desired, dielectric sidewall spacers 535 may be formed on thesidewalls of sacrificial gate structures 556. Sidewall spacers are usedto isolate the gate structure from epitaxial semiconductor material thatmay be grown on the source/drain regions of the fins, as shown in FIG.1A, but spacer material may additionally form on other sidewalls of thegate structure, as shown in FIG. 5C. Sidewall spacers 535 can be formedby any well known technique, such as, for example, by blanket depositinga conformal sidewall spacer dielectric over the substrate, and thenanisotropically etching to remove the dielectric spacer material fromhorizontal surfaces while leaving spacer material on vertical surfaces.The spacers 553 may be silicon nitride, silicon oxide, siliconoxynitride, silicon carbide, CDO or a combination thereof. In anembodiment, an overetch is used to remove spacer material from thesidewalls of fins 512 to enable subsequent growth of an epitaxial layeron the fin surface, doping of the source/drain region, and/or formationof source/drain contacts.

Next, a dielectric material 550 is blanket deposited over the substrate.The dielectric layer is formed to a thickness sufficient to completelycover the substrate including sacrificial gate structure 556. Thedielectric layer 550 is formed of a material that can be selectivelyetched with respect to the sacrificial gate material. That is, thedielectric material is formed of a material whereby the sacrificial gatestructure 556 can be removed without significantly etching away thedielectric layer 550. After blanket depositing the dielectric, thedielectric layer is planarized, for example, by CMP, until the topsurface of the dielectric film is planar with the sacrificial gatestructure 556.

Next, the sacrificial gate structures 556 are etched away to enableformation of gate structures within gate regions 591 and 592.Sacrificial gate structures 556 may be etched using a wet or dry etchprocess. Etching sacrificial gate structures 556 exposes silicon dioxidelayer 525 within gate regions 591 and 592, as shown in FIG. 5D. In anembodiment, the gate dielectric formed in gate region 592 will comprisesilicon dioxide layer 525, but the gate structure formed in gate region592 will not comprise silicon dioxide layer 525. Thus, silicon dioxidelayer 525 is subsequently patterned to remove the portion within gateregion 591, while protecting the portions within gate region 592. Inanother specific embodiment of the invention, all exposed portions ofsilicon dioxide layer 525 are etched away from the surface, and a freshsilicon dioxide layer is either grown from the fins or deposited overthe substrate, in order to have pristine silicon dioxide with which toform active components of a subsequently formed gate structure.

A hardmask 534 is then blanket deposited over silicon dioxide layer 525,as illustrated in FIG. 5E. In an embodiment, hardmask 534 will protectthe portion of silicon dioxide layer 525 within gate region 592 fromexposure to photoresist during etching of the portion of silicon dioxidelayer 525 within gate region 591. Hardmask 534 may comprise, forexample, a work function metal resistant to etching by HF, such as, butnot limited to titanium nitride, tungsten nitride, and tantalum nitride.In an embodiment, hardmask 534 is formed by ALD. Hardmask 534 is formedto a uniform thickness sufficient to protect underlying materials duringthe subsequent etching processes, from 10 to 50 Å thick. In anembodiment, hardmask 534 is 30 Å thick.

Next, hardmask 534 is patterned to remove the portion covering silicondioxide layer 525 within gate region 591, as shown in FIG. 5F. In anembodiment, hardmask 534 is patterned by a photolithography process. Inan embodiment, a photoresist layer 555 is deposited and patterned suchthat hardmask 534 on gate region 592 is covered by photoresist. In anembodiment, hardmask 534 is then etched from regions not covered by thephotoresist, exposing the underlying silicon dioxide layer 525 on gateregion 591. In an embodiment, hardmask 534 is etched using a wet etchprocess which is highly selective to the underlying oxide, such asperoxide and sulfuric acid.

Next, the photoresist layer 545 is removed, leaving hardmask 534 on gateregion 592. In an embodiment, silicon dioxide layer 525 is then etchedfrom gate region 591. By removing photoresist layer 545 prior to etchingsilicon dioxide layer 525, the etching bath used to etch silicon dioxidelayer 525 is not contaminated by the photoresist material. In anembodiment, etching silicon dioxide layer 525 over gate region 591exposes the surfaces of fins 512 and isolation regions 514 in gateregion 591. Any etch selective to the hardmask material over silicondioxide may be used to etch silicon dioxide layer 525. In an embodiment,silicon dioxide layer 525 is etched using HF. In an embodiment, hardmask534 is then removed from gate region 592 to expose silicon dioxide layer525, as shown in FIG. 5H. In an embodiment, hardmask 534 is removed by awet etch process, such as peroxide and sulfuric acid.

The gate structure is then formed by depositing additional gatedielectric layers and gate electrode materials. In an embodiment, a highk dielectric layer 521 is conformally deposited over the substrate,covering the top surface and sidewalls of the fins in gate region 591and conforming to the silicon dioxide layer 525 surface on gate region592. The high k dielectric material is formed by a conformal process,such as CVD or ALD, to ensure contact with the fins in gate region 591or with underlying first silicon dioxide layer 525 in gate region 592.High k dielectric layer 521 may be any suitable high k dielectricmaterial, such as described above with respect to high k dielectriclayer 121 in FIG. 1A. High k dielectric layer 521 may be from 10 to 50 Åthick. In an embodiment, high k dielectric material 521 is 30 Å thick.

Next, the gate electrodes are formed. Each gate electrode may compriseone or more work function metal layers and a fill metal. In anembodiment, work function metal 531 is conformally deposited over thesubstrate. Work function metal 531 is formed by a conformal process,such as CVD or ALD to ensure contact with underlying high k dielectriclayer 521. Work function metal layer 531 may be any suitable workfunction metal, such as described above with respect to work functionmetal layer 131 in FIG. 1A. Work function metal layer 531 may be from 10to 50 Å thick. In an embodiment, work function metal layer 531 is 30 Åthick.

Next, the fill metal 540 material is blanket deposited over workfunction metal 531 to a thickness sufficient to fill the gate structureopenings within gate regions 591 and 592. Fill metal 540 may be formedby any suitable process, such as CVD, ALD, or PVD. The fill metalmaterial may be any suitable gate electrode material, such as describedabove with respect to fill metal 140 in FIG. 1A.

The fill metal 540, work function material 531, and high k dielectriclayer 521 are then chemically mechanically planarized until the topsurface of the dielectric layer 550 is revealed as shown in FIG. 5I.Once the gate electrode material and gate dielectric material arepolished back or removed from the top dielectric material 550, a gatestructure has been formed.

Thus, two transistors 501 and 502 are formed, each with a different gatestructure. In an embodiment, transistor 501 comprises a gate dielectrichaving high k dielectric material 521 and a gate electrode having bothwork function metal 531 and fill metal 540. The gate structure oftransistor 501 may be used for high-performance processor cores. In anembodiment, transistor 502 comprises a gate dielectric having a silicondioxide layer 525 and high k dielectric layer 521 over silicon dioxidelayer 525, and a gate electrode having both work function metal 531 andfill metal 540. As compared to transistor 501, the additional silicondioxide material in the gate dielectric of transistor 502 enables usefor high voltage input-output (I/O) circuits.

FIGS. 6A-G provide an additional embodiment of a method for formingintegrated circuits comprising two types of transistors, where eachtransistor type has a different gate dielectric structure. An integratedcircuit chip typically comprises multiple copies of the same transistorin various locations, however, one of each type of transistor is shownin FIGS. 6A-G for clarity.

A structure comprising substrate 610 with fins 612 separated byisolation regions 614 and gate structure openings above the fins definedby a dielectric 650 having spacers 635 is provided. Methods for formingthe structure are known in the art of semiconductor manufacturing. Thestructure may be formed, for example, by first following the processshown in FIGS. 5A-5D and described above, and then removing the portionsof the silicon dioxide layer 625 that cover gate regions 691 and 693, asshown in FIG. 6A. In an embodiment, silicon dioxide layer 625 is removedfrom gate regions 691 and 693 by wet or dry etch.

Next, a high k dielectric layer 622 is blanket deposited over thesubstrate. High k dielectric material 622 is formed by a conformalprocess, such as CVD or ALD, to ensure contact with the fins in eachgate region. In an embodiment, high k dielectric layer 622 will formpart of the gate dielectric for the transistor formed in gate region693. In an embodiment, high k dielectric layer 622 will be removed fromgate region 691. High k dielectric layer 622 may be any suitable high kdielectric material, such as described above with respect to high kdielectric layer 122 in FIG. 1B. High k dielectric layer 622 may be from10 to 50 Å thick. In an embodiment, high k dielectric material 622 is 30Å thick.

A hardmask 634 is then blanket deposited over high k dielectric layer622, as illustrated in FIG. 6B. In an embodiment, hardmask 634 willprotect the portion of high k dielectric layer 622 within gate region693 from exposure to photoresist during the subsequent etching of high kdielectric layer 622 from gate region 691. Hardmask 634 may comprise,for example, a work function metal resistant to etching by HF, such as,but not limited to titanium nitride, tungsten nitride, and tantalumnitride. In an embodiment, hardmask 634 is formed by ALD. Hardmask 634is formed to a uniform thickness sufficient to protect underlyingmaterials during the subsequent etching processes, from 10 to 50 Åthick. In an embodiment, hardmask 634 is 30 Å thick.

Next, hardmask 634 is patterned to remove the portion covering high kdielectric layer 622 within gate region 691, as shown in FIG. 6C. In anembodiment, hardmask 634 is patterned by a photolithography process. Inan embodiment, a photoresist layer 655 is deposited and patterned suchthat hardmask 634 on gate region 693 is covered by photoresist. Hardmask634 is then etched to expose high k dielectric layer 622 in gate region691. In an embodiment, hardmask 634 is etched using a wet etch processthat is highly selective to the underlying oxide, such as peroxide andsulfuric acid.

The photoresist layer 655 is then removed, leaving hardmask 634 on gateregion 693. The exposed portion of high k dielectric layer 622 over gateregion 691 is then etched to expose the surfaces of fins 612 andisolation regions 614 in gate region 691, as shown in FIG. 6D. Byremoving photoresist layer 655 prior to etching high k dielectric layer622 on gate region 691, the etching bath used to etch high k dielectriclayer 622 is not contaminated by the photoresist material. Any etchselective to the hardmask material over the high k dielectric materialmay be used to etch high k layer 622. In an embodiment, high kdielectric layer 622 is etched using HF. In an embodiment, hardmask 634is then removed from gate region 693 to expose the surface of high kdielectric layer 622, as shown in FIG. 6E. In an embodiment, hardmask634 is removed by a wet etch process, such as peroxide and sulfuricacid.

Next, a high k dielectric layer 621 is conformally deposited over thestructure. In an embodiment, high k dielectric layer 621 will form partof the gate dielectric for each of the transistors formed in gateregions 691 and 693. In gate region 691, high k dielectric material 621covers the fins 612 and isolation regions 614 within the gate structureopening, and in gate region 693, high k dielectric layer 621 conforms tohigh k dielectric layer 622. High k dielectric material 621 is formed bya conformal process, such as CVD or ALD, to ensure contact withunderlying materials in the gate region. In an embodiment, high kdielectric layer 621 has a different composition than high k dielectriclayer 622. In another embodiment, high k dielectric layer 621 has adifferent thickness than high k dielectric layer 622. High k dielectriclayer 621 comprises a high k dielectric material such as described abovewith respect to high k dielectric layer 121 in FIG. 1A. High kdielectric layer 621 may be from 10 to 50 Å thick. In an embodiment,high k dielectric material 621 is 30 Å thick.

Next, a gate electrode is formed. The gate electrode may comprise one ormore work function metal layers and a fill metal. In an embodiment, workfunction metal layer 631 is deposited over the substrate to a uniformthickness. Work function metal layer 631 is formed by a conformalprocess, such as CVD or ALD, to ensure contact with underlying high kdielectric layer 621. Work function metal layer 631 may be any suitablework function metal, such as described above with respect to workfunction metal layer 131 in FIG. 1A. Work function metal layer 631 maybe from 10 to 50 Å thick. In an embodiment, work function metal layer631 is 30 Å thick.

Next, the fill metal 640 is blanket deposited over work function metal631 to a thickness sufficient to fill the gate structure openings overgate regions 691 and 693. Fill metal 640 may be formed by any suitableprocess, such as CVD, ALD, or PVD. The fill metal may be any suitablegate electrode material, such as described above with respect to fillmetal 140 in FIG. 1A.

The fill metal 640, work function material 631, high k dielectric layer621 and high k dielectric layer 622 are then chemically mechanicallyplanarized until the top surface of the dielectric layer 650 is revealedas shown in FIG. 6G. Once the gate electrode materials and gatedielectric materials are polished back or removed from the top ofdielectric material 650, a gate structure has been formed.

Thus, two different transistors 601 and 603 are formed, each with adifferent gate structure. In an embodiment, transistor 601 comprises agate dielectric having high k material 621 and a gate electrode havingwork function metal 631 and fill metal 640. The gate structure oftransistor 601 enables use for high-performance processor cores. In anembodiment, transistor 603 comprises a gate dielectric having a high kdielectric layer 622 and high k dielectric layer 621, and a gateelectrode having work function metal layer 631 and fill metal 640. Thedual high k materials enable use of transistor 603 for low-powercircuits or applications.

FIGS. 7A-E provide an additional embodiment of a method for formingintegrated circuits comprising two types of transistors, where eachtransistor type has a different gate electrode structure. An integratedcircuit chip typically comprises multiple copies of the same transistorin various locations, however, one of each type of transistor is shownin FIGS. 7A-E for clarity.

A structure comprising substrate 710 with fins 712 separated byisolation regions 714 and gate structure openings above the fins,defined by dielectric material 750 and spacers 735 is provided. Methodsfor forming the structure are known in the art of semiconductormanufacturing. The structure may be formed, for example, by firstfollowing the process shown in FIGS. 5A-5D and described above, and thenremoving the portions of the silicon dioxide layer 725 that cover gateregions 791 and 794, as shown in FIG. 7A.

Next, portions of the gate structures are formed by depositing a gatedielectric layer in gate regions 791 and 794. A high k dielectric layer721 is blanket deposited on the structure surface, as illustrated inFIG. 7B, covering fins 712 and isolation regions 714 within gate regions791 and 794. The high k dielectric material 721 is formed by a conformalprocess, such as CVD or ALD, to ensure uniform formation on the surfaceof fins 712. High k dielectric layer 721 comprises a high k dielectricmaterial such as described above with respect to high k dielectric layer121 in FIG. 1A. High k dielectric layer 721 may be from 10 to 50 Åthick. In an embodiment, high k dielectric material 721 is 30 Å thick.

Next, work function metal 732 is blanket deposited over the structure,as shown in FIG. 7B. In an embodiment, work function metal layer 732will form part of the gate electrode for the transistor gate structureformed in gate region 794. In an embodiment, work function metal layer732 will be subsequently removed from gate region 791. In an embodiment,work function metal 732 conforms to the surface of high k dielectricmaterial 721. The work function metal may be deposited by a conformalprocess, such as CVD or ALD. Work function metal layer 732 may be anysuitable work function metal, such as described above with respect toFIG. 1A. In an embodiment, work function metal layer 732 is nitridizedafter deposition to alter the work function of the material. Workfunction metal layer 732 may be from 10 to 50 Å thick. In an embodiment,work function metal layer 732 is 30 Å thick.

Work function metal layer 732 is then patterned to remove the portionwithin gate region 791. In an embodiment, work function layer 732 ispatterned using photolithography. In an embodiment, photoresist layer755 is deposited and patterned such that the portion of work functionmetal layer 732 in gate region 794 is covered by photoresist. In anembodiment, work function metal layer 732 is then etched away from gateregion 791 to expose the underlying high k dielectric material 721, asshown in FIG. 7C. Work function metal layer 732 may be etched witheither a dry etch or a wet etch process.

Next, photoresist 755 is removed and work function metal layer 731 isblanket deposited over the substrate. Work function metal layer 731 isformed by a conformal process, such as CVD or ALD to ensure contact withthe underlying high k dielectric layer 721 on gate region 791 and thework function metal layer 732 on gate region 794. Work function metallayer 731 may be any suitable work function metal, such as describedabove with respect to FIG. 1A. In an embodiment, work function metal 731has a different work function than work function metal layer 732. Workfunction metal layer 731 may be from 10 to 50 Å thick. In an embodiment,work function metal layer 731 is 30 Å thick.

Next, fill metal 740 is blanket deposited over work function metal 731to a thickness sufficient to fill the gate structure openings over gateregions 791 and 794. Fill metal 740 may be formed by any suitableprocess, such as CVD, ALD, or PVD. The fill metal may be any suitablegate electrode material, such as described above with respect to FIG.1A.

Fill metal 740, work function metal 731, work function metal 732, andhigh k dielectric layer 721 are then chemically mechanically planarizeduntil the top surface of the dielectric 750 is revealed as shown in FIG.7E. Once the gate electrode materials and gate dielectric materials arepolished back or removed from the top dielectric material 750, a gatestructure has been formed.

Thus, two different transistors 701 and 704 are formed, each with adifferent gate structure. In an embodiment, the gate structure oftransistor 701 comprises a gate dielectric having high k material 721and a gate electrode having both work function metal layer 731 and fillmetal 740. Transistor 701 may be used for high-performance processorcores. In an embodiment, the gate structure of transistor 704 comprisesa gate dielectric having high k material 721 and a gate electrode havingwork function metal 732, work function metal 731, and fill metal 740.Transistor 704 may be used in low-power circuits or applications.

The above processes, as described with reference to FIGS. 4A-I, 5A-I,6A-G, and 7A-E can be used in combination to form integrated circuitswith three or more types of transistors, each having a different gatestructure.

FIG. 8 illustrates a computing device 800 in accordance with oneimplementation of the invention. The computing device 800 houses a board802. The board 802 may include a number of components, including but notlimited to a processor 804 and at least one communication chip 806. Theprocessor 804 is physically and electrically coupled to the board 802.In some implementations the at least one communication chip 806 is alsophysically and electrically coupled to the board 802. In furtherimplementations, the communication chip 806 is part of the processor804.

Depending on its applications, computing device 800 may include othercomponents that may or may not be physically and electrically coupled tothe board 802. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 806 enables wireless communications for thetransfer of data to and from the computing device 800. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 806 may implement anyof a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 800 may include a plurality ofcommunication chips 806. For instance, a first communication chip 806may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 806 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 804 of the computing device 800 includes an integratedcircuit die packaged within the processor 804. In some implementationsof the invention, the integrated circuit die of the processor includestwo or more fin-based transistors in accordance with implementations ofthe invention. The term “processor” may refer to any device or portionof a device that processes electronic data from registers and/or memoryto transform that electronic data into other electronic data that may bestored in registers and/or memory.

The communication chip 806 also includes an integrated circuit diepackaged within the communication chip 806. In accordance with anotherimplementation of the invention, the integrated circuit die of thecommunication chip includes two or more fin-based transistors inaccordance with implementations of the invention.

In further implementations, another component housed within thecomputing device 800 may contain an integrated circuit die that includestwo or more fin-based transistors in accordance with implementations ofthe invention.

In various implementations, the computing device 800 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 800 may be any other electronic device that processes data.

What is claimed is:
 1. An apparatus, comprising: a first transistor,comprising: a first semiconductor fin with a top, a first sidewall, anda second sidewall opposite the first sidewall; a first gate dielectricstructure that wraps around at least a portion of the first sidewall, atleast a portion of the second sidewall, and at least a portion of thetop of the first semiconductor fin and is in contact with the firstsemiconductor fin, the first gate dielectric structure comprising afirst layer of a first dielectric material having a first thickness andbeing in contact with the top, the first sidewall and the secondsidewall of the first semiconductor fin, and the first gate dielectricstructure comprising a second layer of a second dielectric material on aportion of the first layer of the first dielectric material in contactwith the top, the first sidewall and the second sidewall of the firstsemiconductor fin; a first gate electrode structure that wraps around atleast a portion of the first sidewall, at least a portion of the secondsidewall, and at least a portion of the top of the first semiconductorfin, wherein at least a portion of the first gate dielectric structureis between at least a portion of the first semiconductor fin and the atleast a portion of the first gate electrode structure; and a first ntype source region to a first side of the first gate electrodestructure; and a first n type drain region to a second side of the firstgate electrode structure, the second side of the first gate electrodestructure being opposite the first side of the first gate electrodestructure; and a second transistor isolated from the first transistor,the second transistor comprising: a second semiconductor fin with a top,a first sidewall, and a second sidewall opposite the first sidewall; asecond gate dielectric structure that wraps around at least a portion ofthe first sidewall, at least a portion of the second sidewall, and atleast a portion of the top of the second semiconductor fin and is incontact with the second semiconductor fin, the second gate dielectricstructure comprising a first layer, the first layer of the second gatedielectric structure comprising the first dielectric material and havinga second thickness greater than the first thickness of the first layerof the first gate dielectric structure, and the first layer of thesecond gate dielectric structure in contact with the top, the firstsidewall and the second sidewall of the second semiconductor fin, andthe second gate dielectric structure comprising a second layer, thesecond layer of the second gate dielectric structure comprising thesecond dielectric material on a portion of the first layer of the secondgate dielectric structure in contact with the top, the first sidewalland the second sidewall of the second semiconductor fin; a second gateelectrode structure that wraps around at least a portion of the firstsidewall, at least a portion of the second sidewall, and at least aportion of the top of the second semiconductor fin, wherein at least aportion of the second gate dielectric structure is between at least aportion of the second semiconductor fin and the at least a portion ofthe second gate electrode structure; a second n type source region to afirst side of the second gate electrode structure; and a second n typedrain region to a second side of the second gate electrode structure,the second side of the second gate electrode structure being oppositethe first side of the second gate electrode structure.
 2. The apparatusof claim 1, wherein the first dielectric material comprises silicon andoxygen.
 3. The apparatus of claim 2, wherein the second dielectricmaterial comprises hafnium and oxygen.
 4. The apparatus of claim 2,wherein the second dielectric material comprises a high k valuedielectric material.
 5. The apparatus of claim 1, wherein the firstdielectric material has a first k value and the second dielectricmaterial has a second k value higher than the first k value.
 6. Theapparatus of claim 1, wherein the first gate electrode structurecomprises a first electrode layer comprising titanium and nitrogen andhaving a third thickness, a second electrode layer comprising aluminumand being further from the first semiconductor fin than the firstelectrode layer, and a third electrode layer comprising titanium andbeing further from the first semiconductor fin than the second electrodelayer.